We find that small particles (∼1 nm) of solid argon are densely precipitated in a Pd

40

Ni

20

P

20

metallic glass matrix after argon ion-beam irradiation with an accelerating voltage of 4 keV. This is in sharp contrast to the case of noble-gas implantations into crystalline metals

for which high-energy beam (50–300 keV) has been essential to promote creations of precu

rsor defects

such as voids or vacancy aggregates for initial confinements of noble-gas atoms. Therefore

the present low-energy implantation implies that the argon confinements have occurred at pre-existing low-density regions in the glass matrix

providing an important clue to phenomenological free-volume entities.